Constant temperature cabinet



Jan. 29, 1952 w. VAN GUILDER CONSTANT TEMPERATURE CABINET 6 Sheets-Sheet1 Filed Jan. 13, 1948 QM/fer 26/7 Gza/aer 4P4 4 4/ a; J TTO NZ;

Jan. 29, 1952 w. VAN GUILDER CONSTANT TEMPERATURE CABINET 6 Sheets-Sheet2 Filed Jan. 15, 1948 zo 46 /8 49 5 J5 *1 ia 1 Jan. 29, 1952 w. VANGUILDER 2,533,906

CONSTANT TEMPERATURE CABINET Filed Jan. 13, 1948 6 Sheets-Sheet 3 mp;%/fer )6)? Gui/dew O mE Jan. 29, 1952 w. VAN GUILDER CONSTANTTEMPERATURE CABINET 6 Sheets-Sheet 4 Filed Jan. 13, 1948 %l Ler- Van 5'Jan. 29, 1952 w, VAN GUlLDER 2,583,906

CONSTANT TEMPERATURE CABINET Filed Jan. 13, 1948 6 Sheets-Sheet 6 WagQkfmfek Va Guilder- Q g H-rrchmaY-J Patented Jan. 29, 1952 CONSTANTTEMPERATURE CABINET Walter Van Guilder, River Forest, Ill., assignor toPrecision Scientific 00., Chicago, 111., a corporation of IllinoisApplication January 13, 1948, Serial No. 1,946

12 Claims.

The invention relates to constant temperature cabinets generally, andmore particularly to cabiof the type in which the working chamber ismaintained at a constant temperature by circulating a tempered gaseousheat exchange medium thereabout.

One object of the invention is to provide a cabinet of the above generalcharacter embodying novel features of construction for maintaining thetemperature throughout the working chamber very uniform and withincloser limits than has been practical heretofore.

Another object is to provide a novel heat exchange system for cabinetsadapted to maintain a selected constant and uniform temperature at alltimes in the working chamber of the cabinet, which may be either aboveor below the temperature of the room in which the cabinet is located.

Still another object is to provide a constant temperature cabinetconstructed and arranged so that a gaseous heat exchange medium may becir-- culated over substantially the entire outer surface of the workingchamber.

A more specific object is to provide a constant temperature cabinethaving an inner or working chamber and an outer shell or housing, bothprovided with doors, in which a gaseous exchange medium is normallycirculated over substantially the entire surface of the working chamber,including the door, and embodying novel means for closing off the doorsof the chamber and the housing from the circulating system when theouter door is opened, thereby permitting continued circulation of theheat exchange me dium over the remainder of the working chamber.

A further object is to provide air tempering means for constanttemperature cabinets including elements for heating, cooling,circulating and controlling the temperature of the heat exchange mediumwherein the elements are arranged and mounted in a novel manner whichenables the tempering means to be assembled and tested as a unitindependently of the cabinet and which can be quickly and easilyinstalled in or removed from the cabinet.

It is also an object of the invention to provide various structuralimprovements which simplify manufacture, which facilitate assembly ofthe parts, which materially reduce costs, and which substantiallyimprove the ruggedness and general efficiency of the cabinet.

Other objects and advantages of the inventinn will become apparent fromthe following detail description of the preferred embodimentsillustrated in the accompanying drawings, in which:

Figure l is a perspective view of one form of cabinet embodying thefeatures of the invention.

Fig. 2 is a perspective view of the cabinet shown in Fig. 1, with thetop cover removed.

Fig. 3 is a sectional view of the cabinet shown in Fig. 1, taken in avertical plane extending from the front to the rear of the cabinet.

Fig. 4 is a sectional view taken in a horizontal plane substantially onthe line 44 of Fig. 3.

Fig. 5 is a. fragmentary sectional view taken in a vertical planesubstantially on the line 55 of Fig. 3.

Fig. 6 is a fragmentary sectional view taken in a horizontal plane onthe line 6-6 of Fig. 3.

Fig. '7 is a sectional view of a modified form of the cabinet taken in avertical plane extending from the front to the rear of the cabinet.

Fig. 8 is a sectional view taken in a horizontal plane substantially onthe line 8-8 of Fig. '7.

Fig. 9 is a fragmentary rear view of the cabinet shown in Fig. 7, with apart of the rear wall broken away to show details of construction.

Fig. 10 is an exploded perspective view showing the manner in which theair tempering unit fits into and coacts with the base of the cabinet.

Fig. 11 is a perspective view of the constant level device forregulating the flow of cooling liquid through the cooling coil.

While the invention is susceptible of various modifications andalternative constructions, I have shown in the drawings and will hereindescribe in detail the preferred embodiments, but it is to be understoodthat I do not thereby intend to limit the invention to the specificforms disclosed, but intend to cover all modifications and alternativeconstructions falling within the spirit and scope of the invention asexpressed in the appended claims.

For purposes of illustration, the invention has been shown asincorporated in two cabinets of the type commonly known asbacteriological incubators. The exemplary cabinets are generally alike,except for the manner in which the air tempering means is incorporatedtherein. Thus, each cabinet comprises a generally rectangular outershell or housing In enclosing an inner shell H of sheet metal or othersuitable conductive material which defines a working chamber l2 adaptedto receive the material to be treated. Doors l3 and M respectively inthe front walls of the housing l0 and shell ll provide access to thechamber I2. To maintain a predetermined temperature in the workingchamber, a gaseous heat exchange medium, such as air tempered by athermostatically controlled heating unit l5 or by a cooling coil I5 iscirculated around the inner shell II by a fan or blower l6 driven by amotor M.

In carrying out the invention, provision is made for supporting theshell H with its door 14 and its top, bottom, rear and side walls spacedfrom the door l3 and corresponding walls of the housing Ill.

passage through which the heat exchange medium may be circulated incontact with substantially the entire outer surface of the work chamber.More particularly, the space is partitioned to form an air circulatingpassage including a section extending downwardly along the back andsides of the chamber and a second section extending upwardly along thefront and sides of the chamber. The two sections open respectively intoadjacently disposed communicating compartments which, in the particularcabinet shown in Figs. 1-6. are located at the top of the housing forreceiving the heating unit 15, the coil I5, the thermostatic controlsand the blower l6. Thus even distribution of heat throughout the workingchamber is insured. To minim ze temperature changes in the chamber l2incident to the opening of the cabinet door 13, means is provided forautomatically closing off the front or door portions of the chamber andcabinet from the circulating system when the cabinet door is opened sothat circulation of the heating medium may be maintained over the majorportion of the chamber surface during the open period.

Preferably, the housing 10 is of double walled construction, the spacebetween the walls being filled with suitable insulating material (Fi s.3-6) to reduce heat losses to a minimum. The housing is supported bysuitable legs I! and the too is closed by a removable cover I8. Tosecure the cover [3 in place, angle brackets l9 are spot welded in fourcorners of the cabinet and threaded for the reception of screwsextending through the cover.

In the exemplary cabinet, the door l3 is generally rectangular and, likethe other cabinet elements, is constructed with insulated double walls.The door is supported along one side edge by a suitable hinge 2| (Fig.4) the edge portion of the door being reinforced by an angle member 22to provide a rigid base for the hinge. Similar reinforcement is providedat each side of the housing Ill by angle members 23 mounted between theinner and outer Walls of the same.

The inner shell ll forming the working chamber 12 is simply arectangular sheet metal box having top, bottom, rear and side walls 25,26, 21 and 28. The front wall of the box is open and is arranged to beclosed by the door M as shown in Figs. 3. 4; and 7. A flange 29 (Figs. 3and 7) bent down from the top wall 25 forms a stop for the upper edge ofthe door while a stop for the lower edge of the door is provided by anupstanding flange formed on the forward edge of a tray structure 3|removably supported in the chamber l2. The forward edge of the bottommember 26 of the working chamber is preferably cut off flush with thesurface of the member to facilitate cleaning of the chamber.Perforations in the top and bottom walls 25 and 26 and in the tray 3!permit circulation of air through the working chamber.

As herein shown, the side walls 28 of the shell H are formed withoutturned flanges 32 (Fig. 4)

The space between the walls is partitioned in a novel manner to form a,continuous adapted for attachment to vertical members 33 projecting fromthe interior of the cabinet Ill. The flanges 32 are disposed in a commonplane with the flanges 29 and 30 and with the latter, form a seat forthe door 14.

The door 14, as herein shown, is generally rectangular and comprises achannel member frame 35 fitted with a pane 36 of glass or other suitabletransparent material. Hinges 31 secured to one edge of the door and tothe adjacent wall of the housing I!) support the door so that it may beclosed flush against the flanges 32 to effectually seal the workingchamber. As will be seen by reference to Fig. 4, the reinforcing member23 in the cabinet is extended rearwardly to provide rigid support forthe hinges 31.

Provision is made for supporting the working chamber shell H with itsdoor I4 and its top, bottom, rear and side walls spaced from the door l3and corresponding walls of the housing In and for partitioning theintervening space so as to form a continuous passage for the circulationof the gaseous heat exchange medium around the working chamber. Thesupporting means, in its preferred form, comprises a pair of verticallydisposed channel members 40 (Fig. 6) rigidly secured to opposite sidewalls 28 of the shell II and adapted to interfit with similar y disposedchannels 4| attached to the side walls of the ho sing m. In the cabinetshown in Figs. 1-7, the channels 40 are preferably extended below thebottom wall 26 of the working chamber to rest on the bottom of thehousing and thus hold the shell II in scaced relation with respectthereto. The channel members 40 and 4|, of course, serve to hold theside walls 28 of the shell II in the desired spaced relation to the sidewalls of the housing I0 and, as they extend the full height of theworking chamber, they serve to definethe front and rear sections of acontinuous air circulating passage extending entirely around thechamber. In the particular cabinets shown. the channel members arelocated substantially cen trally of the cabinet structure, thusproviding two passage sections of approximately equal cross sectionalarea.

In the form of the cabinet shown in Figs. 1-6, the inner shell issupported in the housing III with its too wall 25 spaced substantiallybelow the top of the housing, thus providing space for the accommodationof the h ating unit IS, the coil l5, the blower l6, and the motor M.This space is divided by a transverse par itioning member into front andrear compartments 46 and 41 respectively coextensive with the upper endsof the two air circulating passage sections heretofore referred to. Thepartitioning member 45 preferably comprises a flat sheet metal panelmounted with its opposite side edges in abutting engagement with thechannel members 4| which are extended rela ively close to the top of thehousing l0 shown in Figs. 2 and 3. The member is also provided with aflange 48 along its lower edge for attachment to the top wall 25 of theshell H. A flange 49 on the upper edge of the member is adapted toextend over and rest on the upper ends of the channel members 4| whilethe edge portion of the panel is bent up as at 50 for engagement by theunderside of the cover l8. Communication between the compartments 46 and41 is by way of a restricted opening 5| in the partitioning member 45,herein shown as generally circular and located substantially centrallyof the member.

It will be evident from the foregoing that the 55 pattitionlngzsmembcm45: inucoomration; channel members 40 and" H .the'irmer-rwallszofv theIlla andtthe'; shell; II? forming the In: the: present: instance thecoolmg'. coil I8:

' is-rarranged" between: the .heatingIunit-I 5t and .the:

mrkinglchamberz I 2"; define azcommuousmassagel having; two: parallel;sections: extending: respect;- ttvely along: the 1 front and aback of"the: working;

chamber-rand each" including:. subotanti'adlyfiequah' I of. the -1 top;7 side? and bottom: walls: of the-q chamber-:2 The: passage.sectlonsformed:

commumcate'atitheir-uppersand lower ends; com

mtnieaflon 1 at the upper 'end i being; way; of? compartments .46 and:41 through. the restricted I In the :eioeznptary: cabineti. the' blower:I 6 is mounted in" the reariicompartment 241 closely ad:- jaeemitheiopening J; 5.1-:- so as: to draw air. from the forwardicompartmentflfirtoward theirearxof partitioningmember' 45. preferably closely adsjacent the front: face of. the-member with portions ofthercoilextendingtacrossr the opening:

51; Provisiomismadefor circulating a liquid, such cold water, throughthe. coil. whenithe temperaturetofthe chamberrl2 istosbe;

' maintained. at or:below-'thetemperaturc of the;

tho cabinet. To: prevent? the blower. motor." M:

from. inmiencing. the: temperature" oftheicirculatmg air; the housing IIII is :formed to provide j i a motor casing which iscompletely'insulatedf rm: the --interior of the cabinets. ASiShOW'l'I in5,: the' casln'g' includes: an insulated; double walled, boxlikeipartitlonlng: structure 52:- pro iectmgdnwardly from therearrwallof "the housing I!adjacentlthewtop: thereon. Support for tha structureis providedbydepending flanges 58 (F'igs. 3 and -5)-extendin'g along'theside-edges of the-structureand adapted to' rest on the top:

for the worklng chamber is drawn through-the restricted opening 51 intothe blower: chamber 41 and" is dlrected rearwardly r and downwardlyalong the back and-sidesrof theworking-chamber I 2 at the rearsofthechannel members II -and M After-passing along: the bottom of "thechamb'ery the air flows upwardly along the front and side walls of thechamber forwardly: of f the channel I members-to the front-compartmentlat thet'op" of'thecabinet from which it'ls again'drawn by the b lower for recirculation;

Imorder -to -temper the circulating air as requtred for the maintenanceof a predetermined i temperature in: the: working. chamber I 2,. provision is madefor passingsubstantially the entire mass-:- of: air throughthe effective area: of the heating.='unit I5"anditheicoolingcoil Ii.-ineach: circuit through. theaair: passage; To this end;v theeheating:unitzand the .coil' are-'located at the suction side -of. the" blower:I 6 in the path of the-- air stream issuing fromthe retin'fnsection ofthe aha passage. v In: the a embodiment illustrated? in Figs: 1-6'..-0f;thedrawings: .therheatinggmrit' I5.- isr: constructecldn two parts;each" consisting of an: elongated generally: rectangular; frame: 55'(Rigs: 2.- and 3) upon which anrelectrical heating element 56suchasiazlengthsof resistancewire. lsswound.

As shown in-Fig f the drawings; the-frames: Stare mounted in divergingrelation with respect to theopenlng-SI through which the air is drawn by;-the-blower I6; Morerparticularly, the=framcs arew-arrangedsto extendrespectively from" oppos site; ends of? the partltioning member 45: to;a point-closely adjacent thefrontwallbf the he rs-. mg I landsubstantially with; the -center of the opening 51 in the member.Accordingly} air streams 'fiowingenpwardly'along the sides' and; frontof the working chamber aredirected the grids formed onthe'frames 55 by"555 room intwhich.theacabinetiistlocated. To insure:

uniform flow of water throughxthe coil. I5 the: circulating system;includes. flow control means, suchast a constant level: device D (Fig;11),. hereinafter? described in detail. A- valve V is alsoincluded' inthe systemsothat-the flow of? water may be regulated or: discontinuedwhen: thetemperature of..the.cabinet-is to be main! tained above'roomtemperature:

To. maintain: a: desired temperature in the:

.umrkinguchamber, the operation of'the heating;

unit: I5' is". controlled by. adjustabletemper; ature' responsivedevice;such as az'thermostat Sljwhichmay be-of any suitable orwellknown type,arranged to open andxclosejthe electrical.

- circuit 1 of the. .heating'eiement .56 in response "to appropriate:changes in the temperature of the: air circulating .in.the'cabinet. Byreason of its: position" in-the'. air stream; the thermostat. issubjected-.to the-same air." temperatures as the shell II. forming theworkingchamber and. the:

thermostat. is therefore enabled to; perform its Ltemperaturecontrolling function :when the cool-.- ingzcoil I5, is'inoperation as well aswhen the coi'lisidle. ASpShOWIlTin Fig; .3, .thethermostat" 5.! 5 is supported" forwardly of f and adjacent the":

apexof: thez-framesi- 55, in. this instance by. atrearwardly.projecting. bracket 58 mounted the: front wall ofthe housing 7. III.

hereirrshown; adjustment of the thermos statil is* effected by; meansofia rotatable: adejusting rod. 59. projecting" forwardly -through an:aperturein thev'front wall ofjthezhousing III: and provided .1 on; itsouter; end. with a: suitable knob: or handle 60 for manual actuation. Aconvenetionalt switch 62I, conveniently mounted. at the front of" thecabinet; is providedsfor" turning the 1 heafingelementonior; off asrequired. A pilot lamp-6i connected in cirouittwith the heating; unitimay'a'lso besprovided I to; give: axvisual indiecationxwhen i theheating :unit is in' operation;

Its-explained above; the :air after passing" over the :heating; elementI5, and the cooling :coilv I5! is.-:='dra\vn through the restrictedopening 5 I and forced rearwardly along. the top of the working 1chamber, then downwardly along the side and rearwalls.of.theworkingchamber and finally upwardly alongthe side walls. anddoorof thechamber by way of the front and rear sections of the passageformed by. the channel members IT-and M5. Thefrontsection of "thepassagels subdtvlded'into' three parallel branches by the verticalflanges 32 and members 33 heretofore described; One of the branches thusformed extends along the front or' door Ilof the workingchamberwhile theothers extend along the opposite sides of' the chamber;

In=the-normal operation of the cabinet, the circulating air passesfreely through each of the three branch" passages above referred to:thus serving'to apply heat uniformly to substantially'the entire outersurface of the working chamber with the result that the chamberuniformly heated. To prevent excessive temperature changes in thechamber I2 when theouter door" Ilis opened,'- provision" is made forautomatically closing off the branch passage along the front of thechamber from the rest of the circulating system at such times.

In its preferred form, the means for closing ofi the front of thecabinet comprises a pair of dampers or vanes 65, preferably in the formof elongated sheet metal strips respectively SllD'. ported by hinges 66on the housing walls adjacent the top and bottom of the door opening.The vanes are dimensioned to extend entirely across the housing I asshown in Fig. 4 and, when in closed position, to extend over and engagethe top and bottom of the shell II and the upper and lower ends of theflange 32 as shown in broken lines in Fig. 3. The outer marginal edgeportion of each vane may be turned back slightly to provide a roundedcontact surface effective to insure a tight seal between the vane andthe shell. Springs 61 (Fig. 4) yieldably urge the vanes to their closedposition while abutments 68 on the inner side of the door I3 coact withrearwardly projecting arms 69 rigid with the vanes to rock the same toopen position when the door is closed.

With the above arrangement, the vanes 65 are operative automatically inaccordance with the open or closed condition of the door I3 to permit orinterrupt the circulation of air along the front of the chamber I2between the doors I3 and I4. When the door I3 is closed, the heated airis circulated over substantially the entire outer surface of the workingchamber I2, thus providing efficient heat exchange and insuring auniform temperature through the entire chamber. When the door I3 isopened, circulation may be maintained over the major portion of theworking chamber without incurring loss of tempered air and withoutresulting in cooler outer air being drawn into the circulating system.The working chamber is accordingly maintained substantially at thedesired temperature since the application of tempered air to the majorportion of its outer surface is continued.

The constant level device D is provided for maintaining a uniform headof liquid for the coil I5, thereby insuring a steady even flow ofcooling liquid therethrough. As shown in Fig. 11

of the drawings, the constant level device com' prises a pair ofcylindrical receptacles I0 and II arranged one within the other, theinner receptacle II being of smaller diameter and substantially shorterthan the outer receptacle I0. Cooling liquid is introduced into theinner receptacle through the bottom by way of a conduit I2 adapted to beconnected to a suitable liquid source, such as an ordinary water supplysystem.

Opening from the bottom of the inner receptacle is an outlet conduit I3adapted to be connected as by a flexible tube I4 with one end of thecoil I5, the other end of the coil being connected to a suitable drain.A wire strainer I5 enclosing the outlet from the receptacle II preventsforeign material from entering and clogging the coil I5. In theexemplary apparatus, the control valve V is interposed between theoutlet conduit 13 and the connecting tube 14, whereby the rate of flowthrough the coil may be readily controlled. Water is supplied throughthe inlet conduit I2 at a rate in excess of the flow through the coil I5so as to maintain the inner receptacle 'II full at all times. The excesswater admitted to the receptacle spills over the edge into the outerreceptacle I0 and is conducted to the drain by way of a conduit I6.

In the cabinet shown in Figs. 7-10 of the drawings, the housing I0 andthe inner shell II are assembled in the manner above described toprovide a continuous air passage around the working chamber I2. As inthe previously described construction, the passage includes a section atthe rear of the cabinet and a second section at the front of the cabinetboth connecting with a compartment 11 housing the air tempering andcirculating means. In the present instance, the compartment 11 is formedbelow the working chamber I2 by supporting the shell II in spacedrelation to the bottom of the housing I0. Support for the housing isprovided by an angle bar 80 secured at opposite ends to the channelmembers M which are secured to the inner walls of the housing In andserve to define the sections of the air circulating passage asheretofore described.

While air tempering means of any preferred type may be employed, theexemplary cabinet has been shown as equipped with air tempering meansincluding a heating and controlling system of the type disclosed in thecopending application of Frederik Koht Serial No. 4,532, filed January27, 1948, owned by applicants assignee and now abandoned. This systemcomprises a two-stage electrically operated heating element controlledby an adjustable thermally responsive device or thermostat 86 throughthe medium of a pair of relays 8! and 88. The thermostat 86 isadjustable by means of a manually rotatable adjusting rod 89. Pilotlamps 90 and 9| are interconnected with the heater 85 so as to indicatewhen the latter is operating respectively at the high and low heatingrates.

Also included in the air tempering system is a cooling coil 92 similarto the coil I5. Cooling liquid, such as cold water, is supplied to thecoil from the constant level device D which, in this instance, ismounted in a recess 93 (Fig. 7) in the top cover I8 of the housing I0.The device D is connected to the coil by the flexible tube 14 and aconduit 94 in which the valve V is interposed to control the rate offlow through the coil. Adjustment of the valve is effected by means of amanually rotatable stem 95. After passing through the coil, the water isdischarged to the drain through a conduit 96. Circulation of the airover the heating unit 85 and the cooling coil 92 and around the chamberI2 is eifected by a blower I00 similar to the blower I6 and driven by anelectric motor M-I.

To facilitate assembly and testing of the air tempering and circulatingmeans and to permit convenient installation in and removal of the samefrom the cabinet, the various elements are assembled as a compact,self-contained unit on a supporting structure in the form of a drawerI0l adapted to be inserted in the compartment I1. As shown in Fig. 10,the drawer I M comprises a generally rectangular bed I02 of sheet metalor the like having downwardly turned flanges I03 at opposite side edges.An upright panel I04 secured to the front edge of the bed serves as aclosure for the front of the compartment 'II. Preferably, the panel I04is constructedwith double insulated walls similar to those of thehousing I0 to minimize heat losses. As shown in Fig. 'I, the panel I04abuts at its lower and side edges against a suitable gasket I04 mountedon the housing ID to efiectually seal the cabinet. The panel extendsupwardly for engagement with the lower edge of the door I3 and, in theexemplary cabinet, it supports the hinged damper 65 by which the frontof the housing is shut off from the air circulating system when the doorI3 is opened.

Extending transversely across the bed I02 is a partitioning member I05adapted to abut against the angle bar 80 andv inward extensions I06formed on the inner flanges of the channels 4| to divide the compartmentTI into front and rear chambers communicatin respectively with the frontand rear sections of the air circulating passage. A gasket II of felt orother suitable material is interposed between the parts to insure atight joint. Communication between the two chambers formed by thepartitioning member I is provided b an opening I08, herein shown asgenerally circular in form.

The heating unit 85 and the cooling unit 92 are mounted in the frontchamber generally parallel to the partitioning member I05 and suitablyspaced therefrom. Side members E09 extending from the partitioningmember I05 to the front panel I04 and a top member IID extending overthe rear portion of the chamber partially enclose the heating andcooling units and serve to direct the circulating air therethrough onits way to the opening I08.

As in the previously described cabinet, the

thermostat 86 is supported forwardly of the heating unit 85 and itsadjusting rod 89 is extended through the front panel I04 and equippedwith an operating knob Ill (Fig. 7). The valve V is preferably mountedin front of the thermostat with its stem 95 projecting through the frontpanel for manual actuation. As shown in Figs. 7 and 8, the relays 81 and88 are mounted on the front wall of the panel I04 and the pilot lamps 80and 9| are mounted in sockets formed in the panel.

The rear chamber of the compartment 11 accommodates the blower I00 andthe motor M-I. The blower is located adjacent the opening I08 so as todraw air therethrough from the front chamber. This air is then forcedupwardly along the sides and back of the shell II, that is, through. therear section of the air passage and, after passing over the top of theshell, it descends along the front and sides of the shell to the frontchamber of the compartment 11.

To minimize the effect of the heat generated by the motor M-I ontemperature regulation, the motor is completel enclosed in an insulatedcasing II2 mounted on and secured to the bed I02. For ventilatingpurposes the rear end of the motor is arranged to project into a sheetmetal box I I3 mounted on the bed I02 within the casing II2. A gasket II4 of felt or other suitable material tightly fitted around the motorprevents leakage of air between the box and the interior of the casingI02. The box communicates through openings H5 in the bed I02 with an airpassage II6 formed between the bed I02 and the bottom of the housing I0by longitudinally disposed partitioning strips IIl seated in channelsII8 secured to the lower face of the bed. These strips are preferably ofsoft resilient material and in cooperation with similar strips I supportthe drawer and assembled apparatus on the bottom of the housing I0.

The passage H6 is adapted to receive outside air through an opening I2:(Figs. '7 and 10) in the bottom of the housing I0. Air drawn through theopenings II5 into the box H3 and circulated through the motor M-I isdischarged 10 into the casing 2 from the other end of the motor andexhausted to the atmosphere through a series of openings I22 in the backwall of the housin I0. In this way the motor is adequate- 1y ventilatedwithout materially affecting the temperature of the cabinet.

The channel IIG also serves to convey outside air to the tempering meanswhereby an increment of fresh air is continually added to thecirculating air stream. For this purpose the channel is extendedforwardly of the partition I05 and communication with the front chamberof the compartment I1 is provided b a series of openings I23 in the bedI02. In the particular embodiment illustrated the openings I22 arelocated at the rear of and closely adjacent the heating unit 85.

Provision is also made so that the working chamber I2 may be vented tothe atmosphere when desired. For this purpose the top wall 25 of theshell I I is formed with an opening I25 communicating with a vent tubeI25 which is secured to the top wall and extended through an opening I21in the top cover I8 of the housing I0. An adjustable cap I28 ofconventional construction is fitted on the projecting end of the venttube so that the tube can be closed or opened variable amounts toregulate the flow of air therethrough. Leakage of air from thecirculating system through the opening I2! is prevented by an annulargasket I29 mounted on the vent tube for engagement with the innersurface. of the cover I8.

By reason of its novel unitary construction, the air tempering andcirculating means may be completely assembled and tested on the benchbefore it is installed in the cabinet. Assembly and testing is thusfacilitated as all of the parts are readily accessible and are easilyhandled.

.a Installation of the unit in the cabinet is effected 2-15 madesufficiently large to accommodate the bent quickly and easily by simplysliding it into the compartment IT in the base of the cabinet and makingthe necessary water and electric connections. In practice, the flexibletube I4 connecting the constant level device D with the cooling tube 92is made of sufiicient length so that it may be connected with theconduit 94 as by a coupling I30 before the unit is inserted in thecabinet. The conduit 94 may comprise a thinwalled metal tube and ispreferably extended rearwardly of the partition I05, as shown in Fig. 8,to make it readily accessible. The drain conduit 96 may also comprise athin-walled metal tube and is extended rearwardly to project through anopening I3I (Fig. 8) in the rear wall of the housing I0. A plug I32 ofrubber or other suitable material is provided on the conduit to seal theopening against leakage of air from the circulating system.

In order to simplify the connection and disconnection of the motor M-lwhen the unit is installed in or removed from the cabinet, the currentsupply leads for the motor are enclosed in a rigid, rearwardlyprojecting conduit I33 (Fig. 8) terminating in a connector plug I34adapted to seat in an opening I35 in the rear wall in the housing. Topermit the motor to be oiled without requiring removal of the unit fromthe cabinet, a rearwardly extending oil tube I36 is provided andarranged to extend through an opening I31 in the rear wall. of thehousing when the unit is installed. The projecting end of the oil tubeis bent upwardly so that it may be readily filled with oil. The openingI 31 is 11 up end of the tube so that it does not interfere withinstallation or removal of the unit. Suitable plugs or gaskets I38provided on the conduit I33 and the oil tube I36 seal the openings I35and I3! to prevent leakage of air from the circulating system.

It will be apparent from the foregoing, that the invention provides aconstant temperature cabinet of novel and advantageous constructionwhich insures uniform temperature throughout the working chamber andwhich enables the temperature of the chamber to be maintained withinvery close limits. Such temperature uniformity results largely from thenovel arrangement whereby a gaseous heat exchange medium is normallycirculated over substantially the entire outer surface of the workingchamber. Maintenance of uniform temperature is facilitated by theprovision of air tempering means constructed and arranged to act onsubstantially the entire mass of circulating air in each cireuit throughthe apparatus. Abrupt temperature changes in the working chamber areeiTectually avoided by the provision of novel means for automaticallyclosing off the door portion of the cabinet from the circulating systemwhen the outer cabinet door is opened, thus permitting continuedcirculation of the tempered air around the major portion of the workingchamber.

The invention also provides an air tempering and circulating unit ofnovel and advantageous construction which greatly facilitates assemblyand testing and which can be quickly and easily installed in or removedfrom a constant temperature cabinet. Repairs may be made at the benchwhen required, or the defective unit may be returned to the factory forrepair or adjustment. Moreover, should trouble develop while testspecimens are undergoing treatment in the cabinet, the unit may bereadily replaced to maintain the cabinet in operation without seriouslyaffecting the tests.

I claim as my invention:

1. In a constant temperature cabinet, in combination, a generallyrectangular housing having a door opening in its front wall, a hingeddoor for said opening, an open front sheet metal shell enclosed in saidhousing, a hinged panel closing the front of said shell, interengagingflang members on said cabinet and said shell operative to support theshell with its walls in predetermined spaced relation to thecorresponding walls of the housing for the circulation of airthereabout, said flanges defining an air passage extending along thefront of the housing between said door and said panel and communicatingat its upper and lower ends with the space between the shell and housingwalls, and vanes supported in said housing adjacent the upper and lowerends of said shell operable to close off said passage from said space.

2. In a constant temperature cabinet, in combination, a housing having adoor in its front wall, a shell supported in said housing with its wallsspaced from the corresponding walls of the housing, said shell having adoor in its front wall substantially aligned with the door of saidhousing, partitioning means within said housing defining an air passagebetween said doors opening at opposite ends to the space between saidshell and said housing, and vanes operable by the housing door forclosing off said passage from said space when the door is opened.

3. In a constant temperature cabinet, in combination, a housing, a shellsupported in said housing with each of its walls spaced from thecorresponding walls of the housing, said housing and said shell havingdoors in their front walls, partitioning means dividing the spacebetween said shell and the housing into front and rear air passages,means dividing the front air passage into branch passages one of whichincludes said doors, and means for closing said one branch passage fromthe rear passage when the housing door is opened.

4. In a constant temperature cabinet, in combination, a generallyrectangular housing, a generally rectangular shell enclosed within saidhousing to define a working chamber, interfitting channel memberssecured to adjacent walls of said housing and said shell to support theshell in spaced relation to the housing walls, said members additionallyforming a partition dividing the space between the housing and the shellinto parallel air passages communicating at the top and bottom of thehousing, and means for circulating air through said passages.

5. In a constant temperature cabinet, in combination, a generallyrectangular housing, a shell supported in said housing with its wallsspaced from the corresponding walls of the housing to define acompartment communicating with air passages extending along three sidesof the cabinet, said compartment having an outlet located opposite theintermediate one of said sides, means for effecting a flow of airthrough said passages into said compartment and out by way of saidoutlet, an air tempering unit in said compartment including an elongatedheating element, said element being positioned so that the air streamentering the compartment through said passages is directed through theelement, and a cooling coil positioned in the air stream.

6. In a constant temperature cabinet, in combination, a generallyrectangular shell of heat conducting material defining a workingchamber, means cooperating with the walls of said shell to form acontinuous air passage extending around the shell, a partitioning memberextending across said passage and having a restricted opening, blowermeans disposed at one side of said partitioning member for circulatingair through said opening and said passage, a heating unit disposed atthe other side of said partitioning member and positioned to heat thecirculating air, a cooling coil disposed at said other side of thepartitioning member for cooling the circulating air, and a thermostatadapted to control the operation of said heating unit, said thermostatbeing located so that th air impinges upon it after circulating throughsaid passage but before it reaches said heating unit or said coolingcoil.

7. In a constant temperature cabinet, in combination, a housing, a shellof heat conducting material defining a working chamber for the cabinet,means supporting said shell in said housing with its walls inpredetermined spaced relation to the corresponding housing walls so asto form a passage extending entirely around the shell and communicatingat opposite ends with a compartment, partitioning means dividing saidcompartment into two chambers opening respectively to the ends of saidpassage, said partitioning means having an opening providingcommunication between said chambers, air tempering means disposed in oneof said chambers, and air circulating means disposed in the other ofsaid chambers adjacent said opening, said air tempering means, saidpartitioning means and said air circulating means being assembled forinsertion in and removal from said compartment as a unit.

8. In a constant temperature cabinet, in combination, a housing, a shellof heat conducting material defining a working chamber for the cabinet,means supporting said shell in said housing with its walls inpredetermined spaced relation to the corresponding housing walls so asto form a passage extending entirely around the shell and communicatingat opposite ends with a compartment, partitioning means dividing saidcompartment into two chambers opening respectively to the ends of saidpassage, said partitioning means having an opening providingcommunication between said chambers, air tempering means disposed in oneof said chambers, and air circulating means disposed in the other ofsaid chambers adjacent said opening, and a drawer-like structuresupporting said air tempering means, said partitioning means and saidair circulating means for insertion in and removal from said compartmentas a unit.

9. In a constant temperature cabinet, in combination, a sheet metalshell defining a working chamber, a housing enclosing said shell andproviding a closed air circulating passage extending around the shell,said system including a compartment located within said housing andopening at one side thereof, air tempering means including a heatingelement and a cooling coil, air circulating means including a blower anda driving motor therefor, a drawer structure supporting said airtempering and circulating means, said drawer structure being removablyinsertable in said compartment, and a panel at one end of said drawerstructure operative to close the open side of the compartment.

10. In a constant temperature cabinet, in combination, a sheet metalshell defining a working chamber, a housing enclosing said shell andproviding a closed air circulating passage extending around the shell,said passage including a compartment located within said housing andopening at one side thereof, air tempering and circulating means for thecabinet including a heating element, a thermostat for controlling theoperation of said element, a cooling coil, a valve controlling theoperation of said coil, a blower, and a motor for driving said blower, adrawer structure supporting said air tempering and circulating means forinsertion in and removal from said compartment as a unit, said drawerhaving a panel at one end closing the open side of said compartment, andmanually operable means accessible at the front of said panel foradjusting said thermostat and for actuating said valve.

11. In a constant temperature cabinet, in combination, a generallyrectangular shell of heat conducting material defining a, workingchamber, means cooperating with the walls of said shell to form acontinuous air passage extending around said shell, a partitioningmember extending across said passage and having a restricted openingtherein, a blower arranged at one side of said partitioning member todraw air through said opening and circulate it through said passage, airtempering means at the other side of said partitioning member includinga heating unit and a cooling coil disposed in the path 01' thecirculating air adjacent said partitioning member, and means forsupplying a cooling liquid under constant head to said coil.

12. In a constant temperature cabinet, in combination, a generallyrectangular shell of heat conducting material defining a workingchamber, means cooperating with the walls of said shell to form acontinuous air passage extending around said shell, a partitioningmember extending across said passage and having a restricted openingtherein, a blower arranged to draw air through said opening andcirculate it through said passage, air tempering means including aheating unit and a cooling coil disposed in the path of the circulatingair adjacent said partitioning member, a liquid supply system for saidcoil including a constant level device, and a valve for controlling theflow or liquid from said device to said coil.

WALTER VAN GUILDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,848,440 Spitzenberger et a1.Mar. 8, 1932 1,859,613 Bailey May 4, 1932 2,135,181 Jones Nov. 1, 19382,150,064 John et al Mar. 7. 1939 2,233,394 Ashbaugh Mar. 4, 1941

